In the development of orally inhaled and nasal products (OINDPs), a primary focus is achieving deposition at the preferred site within the pulmonary system or nasal cavity. The particle size or droplet size of the delivered drug has a strong influence on this aspect of performance, explaining the reliance on particle size measurement within OINDP research. However, as OINDP performance is refined, more attention is being paid to the path of the drug molecule following deposition. The speed of drug uptake into the bloodstream directly impacts its pharmacodynamic effect and bioavailability and consequently the clinical efficacy and safety of a product. It is therefore becoming increasingly important to have a greater understanding of dissolution behavior at the site of deposition, especially when it comes to demonstrating bioequivalence, a defining element of a generic submission.
